The three-booster rocket — more powerful than any rocket since the Saturn V that took astronauts to the moon in the 1960s and 1970s — lifted off at 3.45 p.m. ET from Kennedy Space Center in Cape Canaveral, Florida. As its second stage sped away from the planet, two of the Falcon Heavy's spent solid rocket boosters fell back to Earth and landed upright, as planned.

One day the Falcon Heavy may be used to ferry colonists to Mars so that humans can become what SpaceX CEO Elon Musk and others have termed a “multiplanet species," capable of surviving if some natural or manmade disaster renders Earth uninhabitable.

The rocket's payload for Tuesday’s flight, however, was a cherry red prototype of a Roadster, an electric vehicle made by Musk’s other company, Tesla. In the car's driver’s seat, a dummy dubbed "Starman" wore a prototype spacesuit designed for use by future astronauts on missions to the International Space Station (ISS) and possibly to Mars.

The rocket and its payload are now embarked on what Musk called a six-hour “grand tour” of Earth’s Van Allen belts, where it will be bombarded by intense radiation from charged particles captured by our planet’s magnetic field. If the second stage of the Falcon Heavy survives the journey, a final burn will propel the Tesla at 24,000 miles per hour into an elliptical orbit around the sun that reaches beyond Mars.

This is the first time a private company has launched anything deep into space.

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Along with the Falcon Heavy, SpaceX is developing a crew-carrying version of its Dragon capsule, which in conjunction with Space’s smaller Falcon 9 rocket has been used to ferry cargo to the ISS since 2012.

Last year, Musk said the Falcon Heavy would be used to send two space tourists in a Dragon capsule on a wild journey around the moon. But on Monday Musk said the rocket would be used strictly for cargo for the foreseeable future.